The quantitative and qualitative analysis of hydrogen cyanide in the gas phase which consists essentially of cyanides or other nitrogen containing materials or mixtures of materials is of very great significance, not only for reasons of environmental protection but also with the follow up industrial processes in which hydrogen cyanide is employed as a reactant or the processes in which hydrogen cyanide containing gases are formed.
Previously hydrogen cyanide or cyanides could be determined quantitatively, e.g. through formation of the complex of silver cyanide and titrimetric detection of the end point as silver iodide, see Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 4, 1st Edition, pages 695-696.
Also specific weight determinations have already been carried out industrially as well as usually qualitatively, hydrogen cyanide determinations in the atmosphere with various test papers, as e.g. the benzidine-copper acetate test or the picric acid-sodium carbonate test (loc. cit.). These types of methods, however, are relatively time consuming and require well trained personnel.
In contrast more favored in use are physical measuring methods, e.g. ultra red spectrometer, gas chromatographs, apparatuses using electrochemical reactions which also are drawn upon for the analysis of hydrogen cyanide, see ACHEMA-Yearbook, 1979.
These physical methods, however, have disadvantages in carrying out in a series since the hydrogen cyanide as is known to polymerize readily, particularly in the presence of basic materials, above all on surfaces made of iron or copper or also on cobalt containing alloys, as well as on glass surfaces or synthetic resin surfaces.
Furthermore, hydrogen cyanide acts corrosively on specific metals which can form the carbide or nitride, as e.g. titanium or molybdenum at elevated temperatures, see Ullmann, Enzyklopedia der technischen Chemie, Vol. 9, 4th Edition, page 657. However, these kinds of metal were frequently used in physical measuring apparatus.
However, a loading of the measuring apparatus or of gas supply parts with polymerizate and/or the partial decomposition of the hydrogen cyanide makes the quantitative detection of the hydrogen cyanide very difficult, if not impossible.
The purpose of the invention therefore is to develop a simple and easily reproducible method of detection for hydrogen cyanide in gases which can also be carried out quantitatively and in series.